(1) Field of the Invention
The present invention relates to a novel maltooligoside derivative, a reagent for determing .alpha.-amylase activity containing the derivative as an effective ingredient and a process for determining efficiently and accurately the .alpha.-amylase activity by the use of the derivative.
(2) Description of the Prior Art
Hitherto, the determination of .alpha.-amylase activity in body fluids such as serum, urine, pancreatic juice and saliva has been very important for clinical diagnoses and is an essential item in the diagnosis of acute or chronic diseases such as hepatitis, pancreatitis, pancreatic carcinoma and epidemic parotiditis.
A variety of methods have hitherto been known as for the method for determining the .alpha.-amylase activity. Among them, a method comprising utilizing as a substrate a compound [having a property of resistance (stability) to hydrolysis by a coupled enzyme] in which a non-reducing end glucose of substituted phenyl maltooligosides is modified by a variety of substituents has been widely used, recently. Said method is one that the compound is cleaved by .alpha.-amylase and the cleavage product is treated with the coupled enzyme, followed by quantitative, colorimetric determination of the resulting substituted phenols directly or, if necessary, after the adjustment of pH, or after the condensation of the phenols.
The substrate used in the aforementioned application is generally required to have the properties that only a single D-glucosidic linkage of the substrate is hydrolyzed, the pattern of action in the hydrolysis and the reaction rate do not vary depending on two .alpha.-amylases (isozymes), the hydrolyzed products are not further hydrolyzed by .alpha.-amylase, the substrate has a high affinity to .alpha.-amylase (that is, a small Km value) and a high hydrolysis rate, and that the substrate has an excellent solubility in water. However, no substrate having a modified non-reducing end which satisfies completely the requirements has hitherto been discovered.
The objects of the present invention are to overcome such defects of conventional reagents for determining the activity of .alpha.-amylase and determining methods using these reagents, and to provide a novel compound suitable as a reagnet permitting efficient and accurate determination of .alpha.-amylase activity and a novel process for determining .alpha.-amylase activity by using the compound as a reagent.
The present inventors have carried out earnest researches for the purpose of accomplishing the aforementioned objects. As a result, they have found that a specified novel maltooligoside derivative is very suitable as a reagent for determining .alpha.-amylase activity and that the aforementioned objects can be achieved by determining .alpha.-amylase activity by the use of the reagent.